r[a_]=2 a^3/(a^2+1)^2;
q[a_]=2 a^3/(a^2-1);
abb=ParametricPlot[{q[a],r[a]},{a,1.01,100},PlotPoints->100,
AxesLabel->{"A","c"},PlotRange->{{0,50},{0,0.8}},ImageSize->{400,300}];